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Related Experiment Videos

Protein phylogenies robustly resolve the deep-level relationships within Euglenozoa.

Alastair G B Simpson1, Andrew J Roger

  • 1Canadian Institute for Advanced Research, Program in Evolutionary Biology, Halifax, Canada NS B3H 4J1. simpson@hades.biochem.dal.ca

Molecular Phylogenetics and Evolution
|March 17, 2004
PubMed
Summary

Phylogenetic relationships within Euglenozoa are clarified using heat shock protein 90 (hsp90) and 70 (hsp70) gene sequences. These analyses reveal a close link between diplonemids and kinetoplastids, challenging previous SSU rRNA findings.

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Area of Science:

  • Protistology
  • Molecular Evolution
  • Phylogenetics

Background:

  • The evolutionary history of Euglenozoa is complex and has been difficult to resolve using traditional methods.
  • Previous studies using small subunit ribosomal RNA (SSU rRNA) data have yielded conflicting results regarding deep-level relationships within this group.

Purpose of the Study:

  • To investigate the phylogenetic relationships among major Euglenozoa groups using novel molecular markers.
  • To resolve the deep-level evolutionary history of Euglenozoa, specifically the placement of euglenids, diplonemids, and kinetoplastids.

Main Methods:

  • Analysis of nuclear-encoded cytosolic heat shock protein 90 (hsp90) and heat shock protein 70 (hsp70) gene sequences.
  • Phylogenetic reconstruction using maximum likelihood (ML) and ML distance methods.

Related Experiment Videos

  • Statistical testing of alternative phylogenetic topologies using approximately unbiased (AU) tests.

    • Main Results:

    • Phylogenetic analyses of hsp90 and hsp70 strongly support a clade uniting diplonemids and kinetoplastids, excluding euglenids.
    • These protein-based phylogenies contradict many previous SSU rRNA studies but align with some recent molecular and morphological data.
    • Re-examination of SSU rRNA data suggests potential instability in inferences from this marker.
    • Protein analyses indicate that bodonids are paraphyletic, with trypanosomatids clustering with specific bodonid clades.

    Conclusions:

    • Heat shock protein data provide robust support for the monophyly of kinetoplastids and diplonemids within Euglenozoa.
    • The findings necessitate a re-evaluation of Euglenozoa evolutionary history, particularly the interpretation of SSU rRNA data.
    • The study refines our understanding of evolutionary patterns within Euglenozoa and related lineages.